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MIC3041 Medical Microbiology > Respiratory Tract Infections > Flashcards

Respiratory Tract Infections Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

How many droplets does a sneeze produce?

A

40,000

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2
Q

How many droplets does coughing produce?

A

3,000

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3
Q

What are the most effective vehicles?

A

Dried droplet nuclei

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4
Q

Why are dried droplet nuclei such effective vehicles?

A

They stay airborne for long period of time

1-10 micrometres in diameter

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5
Q

How long do droplets from Influenza (A and B) persist in the environment?

A

24-72 hours

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6
Q

How long do droplets from SAR-CoV-2 persist in the environment?

A

up to 3 days

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7
Q

How long do droplets from Bordetella pertussis persist in the environment?

A

3-5 days

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8
Q

How long do droplets from Mycobacterium tuberculosis persist in the environment?

A

up to 4 months

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9
Q

What is rhinitis?

A

Infection of the nose

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10
Q

What is sinusitis?

A

Inflammation of the sinuses often following a common cold infection

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11
Q

What is pharyngitis?

A

Infection of the throat

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12
Q

What is laryngitis?

A

Infection of voice box

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13
Q

What is tracheitis?

A

Infection of trachea

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14
Q

What is bronchitis?

A

Infection of bronchi

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15
Q

What is bronchioloitis?

A

Infection of bronchioles

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16
Q

What is pnemonia?

A

Infection of alveoli

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17
Q

What is the first line of defence of the respiratory tract?

A

Mechanisms to remove large incoming particles

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18
Q

What are 4 examples of mechanisms that remove large incoming particles?

A

Nasal hairs trap particles
Saliva flushing oropharynx
Mucus production throughout respiratory tract
Mucociliary system in trachea and bronchi

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19
Q

What happens to the first line of defence if the epithelial cells are damaged?

A

It won’t work, secondary bacterial infections can occur

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20
Q

What can damage epithelial cells of the respiratory tract?

A

bacteria and viruses (e.g. B. pertussis, influenza)
cigarette smoke
pollution

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21
Q

What is the immune response in the alveoli?

A

Small particles (0.05-3 micrometres) are phagocytosed by alveolar macrophages

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22
Q

What do mucosal secretions produce to provide immune protection?

A

Antimicrobial substances

  • lysozyme (lyses bacteria)
  • lactoferrin (iron binding protein that deprives bacteria of the free iron needed for growth)
  • secretory IgA (targets specific organisms)
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23
Q

How are specimens collected from the respiratory tract?

A

Sputum is collected by coughing directly into collection tube or extracted by catheter with suction or during bronchoscopy
Throat or nasopharyngeal swabs
Blood for serological samples

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24
Q

What must be avoided when collecting respiratory samples and why?

A

Salvia because it is a contaminant due to containing millions of bacteria.

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25
Q

How are respiratory tract infections diagnosed phenotypically?

A

Through morphology, physiology of organism

  • gram stain
  • isolation on selective and/or differential media
  • biochemical testing: enzyme production, motility, spore formation
  • antimicrobial sensitivity
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26
Q

How are respiratory tract infections diagnosed immunologically?

A

Serology: characterising antibodies
- IgM detectable 4-7 days
- IgG detectable 2-4 weeks
Commercial antibody-based kits to detect pathogens

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27
Q

How are respiratory tract infections diagnosed genotypically?

A

PCR presence or absence
qPCR amount of pathogen-specific RNA or DNA
High throughput diagnostic chips

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28
Q

Which pathogens adhere to mucosa despite the mucociliary system? (Primary)

A

Influenza
Rhinovirus
Strep. pneumoniae
M. pneumoniae

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29
Q

Which pathogens interfere with the function of cilia? (Primary)

A

Bordetella pertussis
M. pneumoniae
Strep. pneumoniae

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30
Q

Which pathogens resist destruction in alveolar macrophages? (Primary)

A

Legionella

M. tuberculosis

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31
Q

Which pathogens cause local tissue damage? (Primary)

A

Corynebacterium diphtheriae

Strep. pneumoniae

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32
Q

What are secondary respiratory pathogens?

A

They are pathogens that infect the host when the host immune barriers are imparied

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33
Q

Which pathogens infect when there is first an initial infection by a respiratory virus?

A

Staph. aureus

Strep. pneumoniae

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34
Q

Which pathogens infect when there is physiological impairment?

A

Staph. aureus

Pseudomonas spp.

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35
Q

What disease can cause physiological impairment of the respiratory tract?

A

Cystic fibrosis

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36
Q

Which pathogens can infect when the host has chronic bronchitis?

A

Strep. pneumoniae

H. influenzae

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37
Q

Which pathogens can infect when the host is immunocompromised?

A

A. fumigatus

C. neoformans

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38
Q

What is the most deadly lower respiratory tract infection?

A

Pneumonia

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39
Q

What is the most common infection-related cause of death in developing countries?

A

Pneumonia

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40
Q

How many pneumonia deaths per year in children below 5?

A

935,000

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41
Q

What are the causative agents of pneumonia?

A

Bacteria
Viruses
Fungi

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42
Q

How do pathogens reach the lower respiratory tract?

A

Through deep inhalation of aerosols or aspiration of upper respiratory tract flora

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43
Q

What is the main failed defence that leads to pneumonia?

A

Inhibition of ciliary movement due to tobacco, pollution or prior infection

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44
Q

What are the symptoms of pneumonia?

A

Runny nose, congestion, headache, fever

Chest pain, cough, production of discoloured sputum, exudate, difficulty breathing

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45
Q

What is lobar pneumonia?

A

Pneumonia in a distinct region or lobe

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46
Q

What is bronchopneumonia?

A

Diffuse infection of the lung

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47
Q

What is interstitial pneumonia?

A

Invasion of the interstitium

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48
Q

What is a lung abcess?

A

Necrotising pneumonia, destruction of the lung parenchyma

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49
Q

What are the main causes of community acquired pneumonia?

A

Viral
Strep. pneumoniae
H. influenzae

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50
Q

What are the main causes of nosocomial pneumonia?

A

Klebsiella pneumoniae
Staph. aureus (MRSA)
Pseudomonas aeruginosa
P. jirovecii

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51
Q

What is atypical pneumonia?

A

Caused from environmental exposure

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52
Q

What are 3 examples of atypical pneumonia?

A

Legionella pneumophilia from cooling towers, environment
Brucella spp. Coxiella burnetti from infected animals
Aspergillus fumigatus, Crytococcus spp. from mulch and animal droppings

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53
Q

What percentage of hospitalised patients develop pneumonia?

A

1%

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54
Q

What is nosocomial pneumonia associated with?

A

Mechanical ventilation

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55
Q

What is the mortality rate of nosocomial pneumonia?

A

30-50%

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56
Q

What is the origin of nosocomial pneumonia?

A

Polymicrobial origin

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57
Q

How is nosocomial pneumonia diagnosed?

A

Microscopic examination and culture of sputum
X-ray
Bronchoscopy, bronchoalveolar lavage, biopsy

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58
Q

Which part of the respiratory tract does the common cold infect?

A

The upper respiratory tract

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59
Q

How is the common cold diagnosed?

A

Through clinical presentation of symptoms

60
Q

What is the most common cause of the common cold?

A

Rhinoviruses

61
Q

What are the symptoms of the common cold?

A

Rhinorrhoea
Blocked nose
Sore or scratchy throat
Fever

62
Q

Is there a vaccine for the common cold?

A

No

63
Q

What are the main 6 viruses that cause the common cold?

A 
Rhinoviruses
Coxsackie virus A
Parainfluenza virus
Coronaviruses
Adenoviruses
Echoviruses
64
Q

What is the pathogenesis of the common cold?

A
  • Limited virulence mechanisms
  • Symptoms associated with the immune response releasing cytokines and inflammatory mediators
  • Localised inflammation of nasal mucosa leads to rhinorrhoea
  • Can predispose a patient to bacterial secondary infection
65
Q

How is the common cold treated?

A

rest
fluids
antihistamines
decongestants

66
Q

How is the common cold diagnosed in a lab?

A

PCR assays

67
Q

What type of virus is Rhinovirus?

A

Single-stranded RNA virus

Enterovirus genus

68
Q

How many species of Rhinovirus are there?

A

3

A, B and C

69
Q

How many serotypes of Rhinovirus are there?

A

> 165

70
Q

What are the 3 subtypes of Rhinovirus and what cell receptor do they bind to?

A

Major (M): intracellular adhesion molecule 1 (ICAM-1)
Minor (m): low-density lipoprotein (LDL)
RV-C: CDHR3

71
Q

Why is there such diversity in Rhinoviruses?

A

Because their RNA-dependent RNA polymerase is error-prone

It also undergoes recombination with other Rhinovirus species and other species of the genus Enterovirus

72
Q

What are anthroponotic respiratory viruses?

A

They are viruses that infect chimpanzees in Uganda causing severe respiratory disease
Infecting 56 chimps, killing 5
It is closely related to human rhinovirus C45 strains

73
Q

Chimpanzees are homozygous for what allele?

A

CDHR3-Y529

74
Q

Is sinusitis often diagnosed?

A

No

75
Q

What is mild sinusitis usually caused by?

A

viruses

76
Q

What bacteria can cause sinusitis?

A

Strep. pneumoniae

H. influenzae

77
Q

What are the symptoms of sinusitis?

A

Nasal congestion
Headache
Nasal discharge changes during the course of the illness; may become purulent

78
Q

What percentage of acute sore throats are caused by viruses?

A

70%

79
Q

What are the 3 main viral causes of acute sore throats?

A

Adenoviruses
Cytomegaloviruses
Epstein-Barr viruses

80
Q

What are the 2 main bacterial causes of acute sore throats?

A

Strep. pyogenes

Strep. pneumoniae

81
Q

What are the symptoms of acute sore throat?

A

Sore throat
Fever (either low or high grade)
Redness and drainage in the throat

82
Q

Is a laboratory diagnosis required?

A

No

83
Q

What is acute otitis media?

A

An infection of the air-filled space behind the eardrum (the middle ear).

84
Q

What demographic is most likely to suffer from acute otitis media?

A

Young children post cold infection

85
Q

What are the main causes of acute otitis media?

A 
Nasopharyngeal residents migrating along eustachian tube
Strep. pneumoniae
H. influenzae
M. catarrhalis
Strep. pyogenes
86
Q

What are the symptoms of acute otitis media?

A

Bulging ear drum
Persistent fluid in the middle ear
Pus
Intense pain

87
Q

What happens if acute otitis media is not treated adequately?

A

Chronic discharge

Perforated ear drum

88
Q

How is S. pyogenes diagnose?

A

From pharyngeal swab
Rapid antigen test - Ab react to outer carbohydrates of group A streptococci
Culture

89
Q

What type of bacteria is S. pyogenes?

A

gram positive cocci, non-motile, non-sporing

90
Q

Is S. pyogenes fastidious?

A

Yes, requires sheep blood agar. Shows beta-haemolysis due to haemolysins (streptolysins)

91
Q

Is S. pyogenes catalase positive or negative?

A

negative

92
Q

Is S. pyogenes sensitive to bacitracin?

A

yes

93
Q

How is S. pyogenes treated?

A

Penicillin

94
Q

What disease does S. pyogenes cause?

A

Strep throat

95
Q

What are the virulence factors or S. pyogenes?

A

Surface M protein
Hyaluronic acid capsule
Lipoteichoic acid: adhesion to pharynx epithelial cells
Extracellular toxins: streptolysin S and O

96
Q

What encodes pyrogenic exotoxin A (Spe A)?

A

Lysogenic bacteriophage

97
Q

What disease do lysogenic bacteriophage (Strep A/S. pyogenes) cause?

A

Scarlet fever

98
Q

What are the symptoms of Scarlet fever?

A 
Sore throat
headache
fever
swollen glands in neck
sandpaper-like rash
99
Q

What causes Rheumatic fever?

A

S. pyogenes strains that contain M proteins which are antigenically similar to human cell surface antigens - ‘rheumatogenic’

100
Q

What causes damage in rheumatic fever?

A

Cross-reactive antibodies damage organs

101
Q

What is rheumatic heart disease?

A

Disease that arises from multiple infections with different M types of S. pyogenes

102
Q

What does rheumatic heart disease cause?

A

myocarditis and pericarditis in children

damage to heart valves

103
Q

Is there a vaccine for S. pyogenes?

A

None that are commercially available

target conserved region of M protein

104
Q

What does the name Corynebacterium diphtheriae mean?

A 
korynee = club for the club shape of the bacterium
diphtheria = leather hide
105
Q

What type of bacteria is Corynebacterium diphtheriae?

A

aerobic, nonencapsulated, non-spore forming, nonmotile, pleomorphic, gram-positive bacilli

106
Q

What disease does C. diphtheriae cause?

A

Diphtheria

107
Q

What are the symptoms of diphtheria?

A 
Severe sore throat
Fever
Malaise
Swollen lymph nodes
Breathing and swallowing problems
Pseudomembrane covers pharynx and tonsils
108
Q

What is a pseudomembrane?

A

It is a covering of dead cells and bacteria

109
Q

What gene does the corynebacteriophage carry?

A

tox gene which produces an exotoxin

110
Q

How much toxin does 1 corynebacterium produce an hour?

A

5000 molecules

111
Q

Where does the diphtheria toxin go in the body?

A

It is released into the bloodstream and leads to complications in organs including the kidneys and heart

112
Q

What is the structure of the diphtheria toxin?

A

It is a single polypeptide with an A unit and a B unit.

113
Q

What is the cellular process of the diphtheria toxin?

A

B unit binds to host cell, causing partial cleavage and the toxin-receptor complex in internalised.
The A unit dissociates and moves to the cytosol where it blocks protein synthesis.

114
Q

When was diphtheria first described?

A

5th century BC by Hippocrates

115
Q

When was the diphtheria antitoxin discovered?

A

In 1890, Emil von Behring demonstrated serum from animals immunised with C. diphtheriae protected susceptible animals from the diphtheria toxin

116
Q

In what animal is diphtheria antitoxin produced?

A

Horses

117
Q

How is diphtheria diagnosed?

A

Culture of nasal and throat swabs on blood agar

PCR detects toxin producing tox gene

118
Q

How is diphtheria treated?

A

Antitoxin: contains neutralising antibodies
Antibiotics: penicillins and macrolides

119
Q

Is there a vaccine for diphtheria?

A

Yes, diphtheria toxoid vaccine
Infanrix hexa: diphtheria, tetanus, pertussis, hep B, polio, H. influenzae type B
DTaP vaccine: Diphtheria, Tetanus, acellular Pertussis

120
Q

What disease does Bordetella pertussis cause?

A

Whooping cough

121
Q

What is the incubation period of whooping cough?

A

2-21 days

122
Q

What is the initial catarrhal stage of whooping cough?

A

1-2 weeks

123
Q

What is the paroxysmal stage of whooping cough?

A

uncontrollable coughing - “whoops”

paroxysm: convulsive attack

124
Q

What is the convalescent stage of whooping cough?

A

recovering from damage to cilia of respiratory tract epithelial cells

125
Q

What are the consequences of whooping cough in infants?

A

Necrotising bronchitis

Intra-alveolar haemorrhage

126
Q

What are the 11 virulence factors of Bordetella pertussis?

A
  1. Adhesive structure filamentous haemagglutinin (FHA)
  2. Fimbriae 2 & 3 (fim2, fim3)
  3. Pertactin (PRN)
  4. Tracheal colonisation factor (TCFA)
  5. Pertussis toxin (PT)
  6. Adenylate cyclase toxin (ACT)
  7. Tracheal toxin (TCT)
  8. Lipopolysaccharide (LPS)
  9. Dermonecrotic toxin (DNT)
  10. Serum resistance factor
  11. Type III secretion system (TTSS)
127
Q

What does adhesive structure filamentous haemagglutinin do?

A

Surrounds bacterium like a capsule

- can also be secreted in soluble form and can act as a bridge between bacterium and the epithelial cell

128
Q

What do fim2 and fim3 do?

A

adhesion for tracheal epithelial cells

129
Q

What does pertactin do?

A

adhesion

130
Q

What does tracheal colonisation factor do?

A

cytotoxin

adhesion, predominately, in the trachea

131
Q

What does pertussis toxin do?

A

disrupts cellular processes, increases production of mucus

132
Q

What does adenylate cyclase toxin do?

A

cytotoxin that inhibits chemotaxis, phagocytosis, bactericidal killing function of neutrophils

133
Q

What does tracheal toxin do?

A

directly destroys ciliated cells

Stimulates interleukin-1 causing fever

134
Q

What does lipopolysaccharide do?

A

leads to the production of a range of cytokines that inhibit defence functions

135
Q

What does dermonecrotic toxin do?

A

dermal necrosis and vasoconstriction

136
Q

What does serum resistance factor do?

A

potential adhesins, resistance to complement

137
Q

What does type III secretion system do?

A

delivers numerous effector proteins from bacterial cytosol directly into host cells, thus hijacking the intracellular machinery of the infected cells

138
Q

In what cell type can B. pertussis replicate?

A

Macrophages, therefore it can also evade destruction

139
Q

How is whooping cough diagnosed?

A

Often diagnosed based solely on distinctive symptoms
Culture: nasopharyngeal swab
Serology (IgG or IgA) used after 1 month
PCR

140
Q

How is whooping cough treated?

A

Macrolide antibiotics most useful in catarrhal phase

141
Q

When is whooping cough most contagious?

A

In the catarrhal and paroxysmal phases

142
Q

How many cases of whooping cough worldwide in 2014?

A

24.1 million

143
Q

How many children under 5 died from whooping cough in 2014?

A

160,700

144
Q

How many cases of whooping cough in Australia per year?

A

12,000

145
Q

Why is there an increase in cases in Australia over the recent years?

A

Decrease in immunisation rates

146
Q

Is there a vaccine for whooping cough?

A

Yes
Whole cell vaccine: killed B. pertussis cells
Acellular vaccine: toxoid, filamentous haemagglutinin, fimbriae

Infanrix hexa
Boostrix: diphtheria, tenanus, pertussis

MIC3041 Medical Microbiology (11 decks)

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